The invention relates to a process for rotation speed-dependent control and/or diagnosis of a two- or four-stroke combustion engine, in particular its ignition or load state, using a generator which is rotatable in synchrony with the combustion engine and which as a function of the engine rotation position and speed generates alternating voltages which are scanned by a preferably programmable control and used for its power supply, wherein the amounts of alternating voltage amplitudes correspond to a rotation speed level of the combustion engine or rotatable generator. The invention also relates to a control and/or diagnostic arrangement suitable for performance of this process which has a magnetic generator rotatable in synchrony with the revolutions of the combustion engine and is inductively connected with one or more coils. Depending on the rotation speed and rotary position of the combustion engine, the magnetic generator generates alternating voltages which can be detected by a digital electronic preferably programmable control via a scanning device connected with the one or more coils. Furthermore for its power supply the control is coupled with the one or more coils (L1-L4) (i.e. for example magnetic ignition in contrast to battery ignition) and has one or more output interfaces for control and/or diagnosis signals and/or information. The invention also relates to a computer program suitable for the performance of the features according to the invention.
DE 100 24 391 A1 describes a time control for physical events in combustion engines wherein the relevant event is to be synchronised at least partially as a function of the engine load. One example mentioned of such a synchronising event is the ignition control of the combustion engine as a function of the engine load. But also other applications such as the operation of an external display, fuel injection, control of the fuel-air mixture of the engine, control of exhaust emissions etc. should benefit from load-dependent control signals.
According to DE 100 24 391 A1, on a combustion engine the angular velocity of the crankshaft changes during an engine cycle. The information derived from the change in angular velocity of the crankshaft can be used to determine the engine load for most single-cylinder engines and some multi-cylinder engines. In a single-cylinder four-stroke engine the time between successive engine revolutions is measured, beginning with the start of the combustion cycle. The elapsed time of the revolutions containing the combustion and exhaust strokes is shorter and takes place at a higher rotation speed than the time for the subsequent revolution which contains the intake and compression strokes and takes place at a lower rotation speed.
DE 100 24 391 A1 also proposes the use of a microcontroller to determine the difference between the rotation time with the combustion stroke and that with the compression stroke. The engine load is to be a function of this difference. Alternatively the use of a level-sensitive signal detector is suggested which scans an alternating voltage half-wave block. This checks whether the wave block or cycle at half-waves known per se intersects with or reaches a particular point or threshold value. The time between successive intersections is the time for one engine revolution. In this way various engine revolutions are measured, differentiated and used to determine the engine load.
To determine the engine load of a two-stroke engine, according to DE 100 24 391 following the above principle it is also proposed by means of a microcontroller to detect the time between the passing of thresholds by two directly successive pulses of the same polarity. This time in relation to the complete revolution time is regarded as a function of the engine load.
The object of the invention is, in a control and diagnosis process of the type cited initially, to improve the accuracy of detection and allowance for the current engine state, in particular the angular velocity development over one or more revolutions, and hence increase the reliability and operating safety for engine monitoring and controls, in particular engine ignition controls.
The object is achieved by the process given in claim 1 and the control and/or diagnosis arrangement suitable for its performance according to claim 26 and the computer program. Further advantageous embodiments arise from the dependent claims.
As according to this the absolute value is measured in amount at the peak of the alternating voltage amplitude, a direct conclusion of the momentary angular velocity is possible. If this evaluation takes into account the current associated rotary position of the crankshaft of the combustion engine, a precise picture can reliably be obtained of not only the current rotation speed range but also the engine load. With function modules easily implementable in the electronic controls such as weighting factors, filters, analysis algorithms etc., the momentary angular velocity can be used directly and indirectly as data representing the engine load and information for more reliable setting of the ignition timing or advance angle for engine ignition, fuel injection, control of the fuel-air mixture of the combustion engine and exhaust emissions etc.
A particularly great status change in the two- or four-stroke engines and in particular their angular velocity is expected during the compression stroke. This is countered according to an embodiment of the invention in that the coupling of the magnetic generator with the revolutions of the combustion engine is set such that during or in synchrony with the relevant compression stroke, in the alternating voltage at least one of the amplitudes occurs before the engine piston reaches top dead centre. During this phase an amplitude amount with particularly relevant information on the current engine state can be obtained. With this embodiment it is thus possible also to take into account the xe2x80x9cextentxe2x80x9d of the angular velocity loss in the compression phase for further control activities including setting the advance angle, which can be achieved without additional hardware complexity.
This is achieved with the general inventive concept of detecting as an amount the peak voltage of an alternating voltage induced by a rotary magnet wheel of the magnetic generator, for example in coils, and from this concluding the momentary angular velocity. As is known, the peak voltage has a fixed functional correlation with the momentary angular velocity of the magnet wheel.
In order to be able to classify better the angular velocity losses to be expected in the compression cycle in the context of the general engine state, according to a further refinement of the process it is proposed within each engine revolution to determine a mean angular velocity in a manner known per se (see e.g. U.S. Pat. No. 4,924,831, U.S. Pat. No. 5,392,753) by measurement of a duration required for the combustion engine to pass through a particular predetermined reference rotary angle (preferably at least 150xc2x0 of a full revolution). From this information can be obtained on the engine load or volume. As the volume or load increases, in relation to a common rotation speed range, the mean and current momentary angular velocity drift correspondingly further apart; an angular velocity loss is always greater as the volume or load increases, in particular in the compression stroke, immediately before top dead centre. This information can also be used by an electronic control for load-dependent advance angle adjustment or curve reversal, or load-dependent control of other actuators e.g. valves in the carburettor to influence the mixture. With four-stroke combustion engines, alternatively, differences in the peak or amplitude values of the alternating voltage half-waves occurring firstly in the exhaust stroke and secondly in the subsequent working stroke can be calculated alternately and analysed to obtain load information.
It is within the scope of the invention to detect the momentary angular velocity shortly before reaching the rotary or angular position of the magnetic generator wheel in the upper, middle or preferably in the lower rotation speed range, and to determine or readjust the ignition timing subsequently on the basis of this momentary angular velocity value. Thus an optimised advance angle can be determined, preferably in conjunction with preprogrammed advance angle/rotation speed tables, largely unaffected or undistorted by an angular velocity loss above all in the compression phase. A refinement of the general inventive concept lies in particular in that, shortly before reaching the top dead centre where the momentary angular velocity of the compression phase naturally diminishes more or less, this angular velocity loss is detected momentarily and used to adjust the ignition timing. Thus also the requirement for smooth starting of the combustion engine with minimum rotation speed can be taken into account. With the invention namely the advantage can be achieved that easier starting is possible, in particular with small combustion engines. At the same time the user has greater protection against kickback (engine recoil due to over-advanced timing).